Vegetation Restoration Of Degraded Peatland Based On Propagule Reintroduction

The climate change and anthropogenic activities are putting the peatlands at high risk of degradation.Currently,the restoration of degraded peatlands had gained a lot of focus and the restoration is progressing by using two different approaches:natural restoration after rewetting and transplantation of native species for vegetation restoration.In China,there are few studies on peatland vegetation restoration by using Sphagnum.Long-term studies on bryophytes tissue cultures,in vitro culture of Sphagnum and the relatively mature technical system,had been formed,however,there is a lack of study on using plant hormones to initiate callus growth from Sphagnum.The species used for in vitro experiment were as S.magellanicum,S.flexuosum and S.squarrosum,whereas,the in-situ experiment was conducted in Baijianghe peatland in Changbai Mountains.The intermediate Sphagnum was introduced into the species,and the water level elevation and dwarf shrub removal were used in peatland vegetation restoration.There were two experiments in this study:?1?In vitro culture of S.magellanicum was studied to explore the feasibility of indoor cultivation of the Sphagnum propagule used in the restoration of peatland.?2?The effects of water level elevation,dwarf shrub removal and propagation transplant density on the restoration of peatland and its mechanism were studied to provide a basis for the implementation of field restoration.The main results and conclusions are as follows:?1?Antibiotics imposed an inhibitory effect on the germination of Sphagnum spores,and the effect was not obvious in in-vitro culture from spores.Therefore,it is recommended to avoid the usage of antibiotics in culture.?2?The concentration of the medium and the proportion of the elements affected the spore germination and growth of the protonema.The low concentration of Rudolph medium was beneficial for the germination of Sphagnum spores and branching growth of the protonema.Calcium ions affected the elongation of filamentous protonema,and Knop medium containing calcium ions promoted the elongation of the protonema.?3?The auxin analogues 2,4-D and cytokinin 6-BA stimulated the spore germination of Sphagnum flexuosum,while the Sphagnum magellanicum spores were not sensitive to phytohormone stimulation.Both 2,4-D and 6-BA were used to stimulate S.flexuosum and Sphagnum magellanicum,which could not induce callus production.?4?After pulverizing the Sphagnum protonema,it can be subcultured to achieve rapid expansion.After stopping the subculture,the Sphagnum protonema will naturally develop into gametophyte plants.At this stage,phytohormone treatment was applied and it was found that the Sphagnum height was reduced after stimulation with the auxin analogues 2,4-D and cytokinin 6-BA at a concentration of 0.01-0.2 mg·L^-1.?5?Peat blocks and planks were used to block the drainage ditches and to construct dams at different heights.Blocking the drainage ditch is an economical and effective way to regulate the water table depth conditions of degraded peatlands.?6?Water level elevation significantly increased the Sphagnum cover after the end of the two growing seasons.The effect of water level elevation on the growth of Sphagnum was mainly reflected in the colonization stage of the Sphagnum breeding body.A fully humid environment could significantly improve the survival rate of Sphagnum propagules,thus achieving better recovery.?7?Dwarf shrub removal significantly increased the Sphagnum cover after the end of the two growing seasons.The shrub cover blocks the snowfall to form snow cover,therefore,in the process of peatland restoration,the dwarf shrub should be removed so that water level could rise and increase the cover of the Sphagnum.?8?Increasing the transplant density of the propagule significantly increased the Sphagnum coverage after two growing seasons,but increasing the transplant density of the Sphagnum propagules under the dry conditions with low water table or cold conditions during winter decreased the survival rate of Sphagnum.?9?In the field experiment,the elevation of water table level and the removal of small shrubs significantly increased the coverage of herbaceous plants in the plot,but the introduction of Sphagnum propagules had no significant effect on the growth of herbaceous plants.In summary,the use of Rudolph medium for germination of Sphagnum spores to obtain protonema,followed by a subculture of Sphagnum protonema achieved the purpose of rapid expansion of Sphagnum propagules.The rising of water level and removal of dwarf shrubs in the peatland restoration was beneficial to the growth of Sphagnum,and it is more effective to control the transplant density of Sphagnum propagules around 1:10.